Extracting ordinary and extraordinary optical characteristics for critical dimension measurement of anisotropic materials

ABSTRACT

Methods and apparatus for measuring a critical dimension of an optically-anisotropic feature, including extracting a number of values each descriptive of the optically-anisotropic feature, including values corresponding to ordinary and extraordinary measurements of one or more optical characteristics of the optically-anisotropic feature. The optical characteristics can include the index of refraction and/or the extinction coefficient of the optically-anisotropic feature, among others. Additionally, the values can be input into an optical critical dimension (OCD) measurement model, such that the critical dimension can be verified via optical measurement based on the OCD measurement model. The optical measurement of the critical dimension can also be verified via scanning electron microscope (SEM) measurement. Furthermore, the optically-anisotropic feature may have a substantially amorphous composition, such as amorphous carbon, including where the optically-anisotropic feature is that of a hardmask substantially comprising amorphous carbon or otherwise having a substantially amorphous composition.

CROSS REFERENCE

This application claims priority to U.S. Patent Application Ser. No.60/792,560 filed on Apr. 17, 2006 which is hereby incorporated byreference.

BACKGROUND

Hardmasks and other photomasks are often utilized in lithography systemsto manufacture the ICs, where successful production can require featureson such photomasks have desired and uniform sizes. Accordingly,photomask manufacturers routinely evaluate feature sizing performance bymeasuring specific features in order to ensure that the photomasksinclude features that have the desired and uniform sizes. The featuresthat are evaluated are generally referred to as critical dimensions(CDs), and are measured via optical systems and/or scanning electronmicroscopes (SEMs).

Optical metrology tools include reflectometers, ellipsometers,spectroscopic reflectometers, spectroscopic ellipsometers, polarizedbeam reflectometers, polarized beam spectroscopic reflectometers,scatterometers, spectroscopic scatterometers and optical CD measurementtools. Optical CD (OCD) measurement is useful because often only onemeasurement is required to analyze CDs, profiles, thicknesses, andsidewall angles without fracturing the wafer. However, as feature sizeshave decreased below resolution limits of many OCD measurement tools,the use of SEMs has increased. Nonetheless, multiple optical and/orelectron microscope instruments can be combined on a common platform tocomprise a single metrology instrument that incorporates multiplespectroscopic metrology capabilities. In such arrangements, one or moreprocessors may be utilized to analyze output signals generated byvarious detectors, processing the output signals individually or incombination to evaluate the characteristics of a sample.

Hardmasks formed by ash removable deposition (ARD) processing,particularly hardmasks comprising amorphous carbon, has recently gainedpopularity as a new approach for IC patterning. Amorphous carbon has alow etching rate, thus making its utilization beneficial when subsequentprocessing includes oxide or silicon dry etching. Additionally,amorphous carbon is easily removed by O₂ plasma. Hence, patterning andstripping such hardmasks have little impact on profiles and CDs offeatures defined in underlying layers. Amorphous carbon also provides ahigh extinction coefficient k, which is beneficial during lithographicpatterning. However, current optical measurement methods, such asellipsometry and reflectometry, only extract the ordinary refractiveindex n and extinction coefficient k which are insufficient toaccurately characterize amorphous carbon and other optically anisotropicmaterials.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures may not be drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic view of a light beam incident on a sample,demonstrating aspects related to the prior art and the presentdisclosure.

FIG. 2 is another schematic view of a light beam incident on a sample,demonstrating aspects related to the prior art and the presentdisclosure.

FIG. 3 is a schematic view of at least a portion of one embodiment ofapparatus according to aspects of the present disclosure.

FIG. 4 is a schematic view of at least a portion of another embodimentof apparatus according to aspects of the present disclosure.

FIG. 5 is a schematic view of at least a portion of another embodimentof apparatus according to aspects of the present disclosure.

FIG. 6 is a schematic view of at least a portion of another embodimentof apparatus according to aspects of the present disclosure.

FIG. 7 is a flow-chart diagram of at least a portion of one embodimentof a method according to aspects of the present disclosure.

FIG. 8 is a flow-chart diagram of at least a portion of anotherembodiment of the method shown in FIG. 7.

FIG. 9 is a schematic view of at least a portion of one embodiment ofapparatus according to aspects of the present disclosure.

FIG. 10 is a schematic view of at least a portion of another embodimentof the apparatus shown in FIG. 9.

FIG. 11 is a schematic view of at least a portion of yet anotherembodiment of the apparatus shown in FIG. 9.

FIG. 12 is a flow-chart diagram of at least a portion of one embodimentof a method according to aspects of the present disclosure.

FIG. 13 is a flow-chart diagram of at least a portion of anotherembodiment of the method shown in FIG. 12.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof various embodiments. Specific examples of components and arrangementsare described below to simplify the present disclosure. However, theseare merely examples, and are not intended to be limiting. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed. Moreover, theformation of a first feature over or on a second feature in thedescription that follows may include embodiments in which the first andsecond features are formed in direct contact, and may also includeembodiments in which additional features may be formed interposing thefirst and second features, such that the first and second features maynot be in direct contact.

Ellipsometry and/or reflectometry are often employed to characterize theoptical constants and thickness of thin films, including hardmasks andother photomasks. Such techniques are sensitive to several materialcharacteristics, such as layer thickness, optical constants (refractiveindex and extinction coefficient), surface roughness, composition, andoptical anisotropy. For example, these characteristics are determinablefrom transmission and reflection intensity data obtained via utilizationof a reflectometer, and/or transmission, reflection intensity andellipsometry obtained via utilization of an ellipsometer.

Referring to FIG. 1, illustrated is a schematic of a beam of light 10incident on a sample 20 at an angle of incidence Φ_(i), demonstratingthe resulting transmitted beam 30 and reflected beam 40. The angle ofincidence Φ_(i) is defined as the angle between the direction of theinput beam 10 and the direction normal to the sample 20 (designated inFIG. 1 by reference numeral 25). At the boundary between mediums (theboundary between the sample 20 and the air or other ambientenvironment), part of the input beam 10 will be reflected from thesample 20 as the reflected beam 40 at angle Φ_(r), while another part ofthe input beam 10 will be transmitted through the sample 20 as thetransmitted beam 30 at angle Φ_(t). Snell's law requires that all threeof the input beam 10, the transmitted beam 30, and the reflected beam 40be in the plane of incidence 50. The plane of incidence 50 is defined asthat plane which contains the input beam 10, the output beams 30 and 40,and the normal direction 25 of the sample 20.

The measurements described above may acquire the transmission intensityratio T and reflection intensity ratio R over a given range ofwavelengths. T is defined as the ratio of the transmitted lightintensity I_(t) and the incident light intensity I_(i), as shown inEquation (1):T=I _(t) /I _(i)  (1)

R is defined as the ratio of the reflected light intensity I_(r) and theincident light intensity I_(i), as shown in Equation (2):R=I _(r) /I _(i)  (2)

Ellipsometry measures the change in polarization state of lightreflected from the surface of a sample. The measured values areexpressed as Ψ and Δ. These values are related to the ratio of Fresnelreflection coefficients, R_(p) and R_(s), for p- and s-polarized light,respectively, by Equation (3):tan(Ψ)e ^(iΔ) =R _(p) /R _(s)  (3)

Because ellipsometry measures the ratio of two values, it can be highlyaccurate and very reproducible. From Equation (3), the ratio is seen tobe a complex number containing “phase” information in Δ, which makes themeasurement very sensitive.

Referring to FIG. 2, illustrated is a schematic of a linearly polarizedinput beam 60 that is converted to an elliptically polarized reflectedbeam 70. For an angle of incidence Φ_(i) greater than 0° and less than90°, p-polarized light and s-polarized will be reflected differently.

The coordinate system used to describe the ellipse of polarization isthe p-s coordinate system. The p-direction is taken to be perpendicularto the direction of propagation and contained in the plane of incidence50. The s-direction is taken to be perpendicular to the direction ofpropagation and parallel to the surface of the sample 20.

Optical constants define how light interacts with a material. Thecomplex refractive index is a representation of the optical constants ofa material, as shown in Equation (4):ñ=n+ik  (4)

The real part, or index of refraction n, defines the phase velocity oflight in material, which is defined by Equation (5):ν=c/n  (5)where ν is the speed of light in the material and c is the speed oflight in vacuum. The imaginary part, or extinction coefficient k,determines how fast the amplitude of the wave decreases. The extinctioncoefficient k is directly related to the absorption of a material and isrelated to the absorption coefficient α by Equation (6):α=4πk/λ  (6)where α is the absorption coefficient and λ is the wavelength of light.

There are many ways to measure the reflection and transmissionproperties described above. One example is by polarization-sensitivereflectivity. FIG. 3 is a schematic view of at least a portion of oneembodiment of apparatus 100 that may be employed inpolarization-sensitive reflectivity in accord with one or more aspectsof the present disclosure. The apparatus 100 includes a polarizer 105through which an input beam 110 passes prior to incidence on the sample20. The apparatus 100 also includes a polarizer 115, often referred toin this context as the “analyzer,” through which passes the resultingreflected beam 120. A detector 130 is positioned to detect one or morecharacteristics of the reflected beam 120, such as intensity and/orphase, whether constant or time-dependent. The detector 130 may beintegral to the apparatus 100, as depicted in FIG. 3, or otherwiseassociated with the apparatus 100.

After polarization via the polarizer 105, the input beam 110 interactswith the sample 20 at an angle of incidence Φ_(i). The reflected beam120 is then re-polarized via the analyzer 115 before its intensity isdetected. At a large angle of incidence Φ_(i), there is a significantdifference in the reflectance for s- and p-polarized light, so there aretwo pieces of information that can be obtained about the sample 20 ateach wavelength of the input beam 110, as represented by Equations (7)and (8):R _(p) =r _(p) r _(p)*  (7)R _(s) =r _(s) r _(s)*  (8)

These quantities are measured by aligning the polarizer 105 and theanalyzer 115 in either the s or the p orientation. The apparatus 100 canalso be used as an example for the calculation using Mueller matrices.For the p measurement, the polarizer 105 and the analyzer 115 arealigned parallel to the plane of incidence 125, such that:θ₀=θ₁=0°  (9)where θ₀ is the polarization angle of the polarizer 105 (e.g.,orientation of the fast axis relative to a principal frame of reference)and θ₁ is the polarization angle of the analyzer 115 (e.g., orientationof the fast axis relative to the same principal frame of reference).Subsequent Mueller matrix multiplication yields:I_(p)=I₀R_(p)  (10)

For the s measurement, the polarizer 105 and the analyzer 115 arealigned perpendicular to the plane of incidence 125, such that:θ₀=θ₁=90°  (11)andI_(s)=I₀R_(s)  (12)

Another technique for measuring the above-described reflection andtransmission properties in accord with one or more aspects of thepresent disclosure is rotating analyzer ellipsometry (or rotatingpolarizer ellipsometry). FIG. 4 is a schematic view of at least aportion of one embodiment of apparatus 150 that may be employed inrotating analyzer ellipsometry in accord with one or more aspects of thepresent disclosure. The apparatus 150 includes a polarizer 155 throughwhich an input beam 160 passes prior to incidence on the sample 20. Theapparatus 150 also includes an analyzer 165 through which passes theresulting reflected beam 170. A detector 180 is positioned to detect oneor more characteristics of the reflected beam 170, such as intensityand/or phase, whether constant or time-dependent. The detector 180 maybe integral to the apparatus 150, as depicted in FIG. 4, or otherwiseassociated with the apparatus 150.

The analyzer 165 is configured to be physically rotated so that theazimuthal angle of the analyzer 165 is given by:θ₁=ωt  (13)

Alternatively, where the polarizer 155 is configured to be physicallyrotated instead of the analyzer 165, such that the azimuthal angle ofthe polarizer 155 is given by:θ₀=ωt  (14)

The intensity of the reflected beam 170 after passing through theanalyzer 165, as detected by the detector 180, is given by:I(t)=I _(dc)[1+a ₁ cos(2ωt)+a ₂ sin(2ωt)]  (15)whereI _(dc)=1−N cos(2θ_(p))  (16)a ₁=[cos(2θ_(p))−N]/[1−N cos(2θ_(p))]  (17)a ₂ =[C sin(2θ_(p))]/[1−N cos(2θ_(p))]  (18)The associated ellipsometry parameters N and C in Equations (16)-(18),as well as ellipsometry parameter S, are represented by:N=cos(2ψ)  (19)C=sin(2ψ)cos(Δ)  (20)S=sin(2ψ)sin(Δ)  (21)The angles ψ and Δ are the traditional ellipsometry parameters, whichare defined as:ρ=r _(p) /r _(s)=tan(ψ)exp(iΔ)=[C+iS]/[1+N]  (22)

In one embodiment, the signal is normalized to the I_(dc) term, and maynot be directly measured. The two Fourier components a₁ and a₂ arefunctions of the fixed polarizer angle and the sample parameters N andC.

Another technique for measuring the above-described reflection andtransmission properties in accord with one or more aspects of thepresent disclosure is nulling ellipsometry. FIG. 5 is a schematic viewof at least a portion of one embodiment of apparatus 200 that may beemployed in nulling ellipsometry in accord with one or more aspects ofthe present disclosure. The apparatus 200 includes a polarizer 205 and acompensator 210 through which an input beam 215 passes prior toincidence on the sample 20. The apparatus 200 also includes an analyzer220 through which passes the resulting reflected beam 225. A detector230 is positioned to detect one or more characteristics of the reflectedbeam 225, such as intensity and/or phase, whether constant ortime-dependent. The detector 230 may be integral to the apparatus 200,as depicted in FIG. 5, or otherwise associated with the apparatus 200.

Measurements may be made with the apparatus 200 by rotating theazimuthal angle of the polarizer 205 (θ₀) and the azimuthal angle of theanalyzer 220 (θ₁) to minimize the intensity of light incident upon thedetector 230. Nulling ellipsometer measurements are made by fixing theazimuthal angle of the compensator 210, such as at θ_(c)=45°, and thedegree of retardation of the compensator, such as at δ=π/2, althoughother values are also within the scope of the present disclosure. Underthese assumptions, the intensity at the detector 230 is given by:I=0.25I ₀ R{1−N cos(2θ₁)+sin(2θ₁)[C sin(2θ₀)+S cos(2θ₀)]}  (23)

In one embodiment, the compensator 210 is designed for a specificwavelength (such as 633 nm) and its retardation is about (or precisely)π/2. However, other values are also within the scope of the presentdisclosure.

Another technique for measuring the above-described reflection andtransmission properties in accord with one or more aspects of thepresent disclosure is rotating-analyzer ellipsometry with a compensator.Standard rotating-analyzer ellipsometers may be insensitive to the Sparameter, and therefore not be able to measure Δ accurately when Δ isnear 0° or 180°. One solution to this is to include a compensatingelement in the light path. FIG. 5 may also depict a rotating-analyzerellipsometer 200 with a compensating element 210 after the polarizer205, if modified in the respect that the analyzer 220 is rotated. Thecompensator 210 may be a quasi-achromatic compensator, where δ˜π/2.Assuming that the polarizer 205 is set at 45° with respect to the fastaxis of the compensator 210, the intensity at the detector 230 is thengiven by:I _(dc)=1−N sin(2θ_(c))cos(δ)  (24)wherea ₁=[−sin(2θ_(c))cos(δ)−N]/[1−N sin(2θ_(c))cos(δ)]  (25)a ₂ =[C cos(2θ_(c))cos(δ)−S sin(δ)]/[1−N sin(2θ_(c))cos(δ)]  (26)If the phase retardation of the compensator 210 is given by δ=π/2, thena₁=−N and a₂=−S. However, if the phase retardation of the compensator210 is δ=0, the results are the same as for the rotating analyzerellipsometer, described above.

Some ellipsometers use the scheme of nulling ellipsometers where the twopolarizers (e.g., polarizer 205 and analyzer 220) are fixed and thecompensator (e.g., compensator 210) is rotated. In such an arrangement,the light intensity incident upon the detector 230 becomes a function oftime, much like the rotating analyzer ellipsometer described above.Because the compensator 210 is rotating between the sample 20 and thepolarizer 205, there are two frequency components: 2ωt and 4ωt. Theintensity of the light beam incident upon the detector 230 is then givenby:I=I _(dc) +a _(2S) sin(2ωt)+a _(2C) cos(2ωt)+a _(4S) sin(4ωt)+a _(4C)cos(4ωt)  (27)The values of the five coefficients shown in Equation (27) depend uponthe retardation of the compensator δ, which will also be a function ofwavelength, as well as the azimuthal angles θ_(p) and θ_(a). For this tobe a complete ellipsometer (that is, where N, S and C are all measured),θ_(a) must not be close to 0° or 180°. If it is assumed that θ_(a)=45°,then the five coefficients are given by:I _(dc)=1+0.5[1+cos(δ)][C sin(2θ_(p))−N cos(2θ_(p))]  (28)a _(2S) =S sin(δ)cos(2θ_(p))  (29)a _(2C) =S sin(δ)sin(2θ_(p))  (30)a _(4S)=0.5[1−cos(δ)][C cos(2θ_(p))−N sin(2θ_(p))]  (31)a _(4C)=−0.5[1−cos(δ)][C sin(2θ_(p))+N cos(2θ_(p))]  (32)Accordingly, this ellipsometer is capable of measuring N, S and C forall values of θ_(p).

Another technique for measuring the above-described reflection andtransmission properties in accord with one or more aspects of thepresent disclosure is polarization modulation ellipsometry. Polarizationmodulation ellipsometers are generally defined as ellipsometers that usea modulation technique other than the physical rotation of one or moreoptical elements. FIG. 6 is a schematic view of at least a portion ofone embodiment of apparatus 250 that may be employed in polarizationmodulation ellipsometry in accord with one or more aspects of thepresent disclosure. The apparatus 250 includes a polarizer 255 and aphotoelastic modulator (PEM) 260 through which an input beam 265 passesprior to incidence on the sample 20. The apparatus 250 also includes ananalyzer 270 through which passes the resulting reflected beam 275. Adetector 280 is positioned to detect one or more characteristics of thereflected beam 275, such as intensity and/or phase, whether constant ortime-dependent. The detector 280 may be integral to the apparatus 250,as depicted in FIG. 6, or otherwise associated with the apparatus 250.

The PEM 260 is generally used to generate a time-dependent polarizationstate, although it is also possible to use electro-optic modulators.Although there are several designs within the scope of the presentdisclosure, all share a common description. The PEM 260 is atime-dependent compensator, where the retardation δ(t)=A sin(ωt), themodulation amplitude A being proportional to the driving force of themodulator. In its operation, an optical element is set into physicaloscillation by some external driving force. If the optical element ofthe PEM 260 is momentarily in compression, then the refractive indexalong the compressive direction is higher than the refractive indexwould be in the unstrained optical element, while the refractive indexperpendicular to the compressive direction is lower. Similarly, if theoptical element of the PEM 260 is momentarily in expansion, then therefractive index along the expansive direction is lower, but therefractive index perpendicular to the expansive direction is higher thanin the unstrained optical element. The Mueller matrix for the PEM 260 isthe Mueller matrix for a compensator where δ(t)=A sin(ωt).

The basis functions for rotating element ellipsometers are of the formsin(nωt) and cos(nωt), where n is an integer, such that standard Fourieranalysis can be used. The basis functions for polarization modulationellipsometers are of the form X=sin[A sin(ωt)] and Y=cos[A sin(ωt)].These basis functions can be expressed in terms of an infinite series ofsines and cosines, using integer Bessel functions as coefficients:

$\begin{matrix}{X = {{\sin\left\lbrack {A\;{\sin\left( {\omega\; t} \right)}} \right\rbrack} = {2{\sum\limits_{j = 1}{{J_{{2j} - 1}(A)}{\sin\left\lbrack {\left( {{2j} - 1} \right)\omega\; t} \right\rbrack}}}}}} & (33) \\{Y = {{\cos\left\lbrack {A\;{\sin\left( {\omega\; t} \right)}} \right\rbrack} = {{J_{0}(A)} + {2{\sum\limits_{j = 1}{{J_{2j}(a)}{\cos\left( {2j\;\omega\; t} \right)}}}}}}} & (34)\end{matrix}$

As seen from Equations (33)-(34), the Y basis function has no dc term ifJ₀(A)=0, which happens if the modulation amplitude A=2.4048 radians. Inone embodiment, the modulation amplitude A is set to this value tosimplify the analysis. In operation, the polarizer is set to ±45° withrespect to the PEM and the analyzer is set to ±45° with respect to theplane of incidence. Assuming both are +45°, the intensity incident uponthe detector 280 can be given as:I(t)=I ₀(R/4){1−SX−[cos(2θ_(c))C+sin(2θ_(c))N]Y}  (35)

From this expression, it can be seen that two sample parameters can bemeasured at any one time. The sin(ωt) Fourier coefficient is alwaysproportional to the S parameter, and the cos(2ωt) is proportional toeither N or C, depending on the azimuthal angle of the PEM 260 (θ_(c)).

It is possible to make a single PEM ellipsometer complete—that is, tomeasure N, S and C. One way to do this is via a two-channelspectroscopic polarization modulation ellipsometer (2-C SPME), where thesingle analyzer polarizer is replaced with a Wollaston prism. TheWollaston prism deviates the incident light beam into two mutuallyorthogonal linearly polarized light beams, both of which are detectedwith the 2-C SPME. If the azimuthal angle of the PEM is set toθ_(c)=±22.5° and if the Wollaston prism is set at θ_(a)=±45°, then it ispossible to measure N, S and C.

Referring to FIG. 7, illustrated is a flow-chart diagram of at least aportion of one embodiment of a method 300 according to aspects of thepresent disclosure. The method 300 may be employed or performed withmeasurement apparatus having one or more aspects similar to thosedescribed above with respect to FIGS. 3-6. In one embodiment, the method300 is for extracting ordinary (p) and extraordinary (s) opticalcharacteristics from an anisotropic sample (or portion thereof). Forexample, the sample may be or include a hardmask substantiallycomprising amorphous carbon and/or other anisotropic materials, and themethod 300 may be employed to extract ordinary and extraordinary indicesof refraction and/or extinction coefficients, which may then be employedto determine thickness, width, and/or other characteristics of thehardmask, possibly including characteristics other than dimensions. Theextracted ordinary and extraordinary characteristics may also oralternatively be employed in optical and/or other CD measurementmodeling and/or systems.

The method 300 includes a step 310 in which an anisotropic hardmask isformed by conventional or other means. For example, the hardmask may beformed by spin-on coating of an anisotropic photoresist material, suchas amorphous carbon. The layer of photoresist may then be patterned anddeveloped for subsequent use during etching of underlying layers. Thephotoresist may undergo one or more thermal treatments, such as to bakeout any solvent and/or adjust selectivity.

In one embodiment, the hardmask is formed by or in conjunction with adual deposition station processing chamber. However, the followingdescription is merely exemplary of the aspects within the scope of thepresent disclosure, and should be interpreted accordingly. For example,flow rates may be total flow rates and, accordingly, may be divided intwo to describe the process flow rates at each deposition station in adual-station chamber. Additionally, or alternatively, single depositionchambers (such as the DxZ processing chamber that is commerciallyavailable from APPLIED MATERIALS, INC., of Santa Clara, Calif.) may beemployed during the processing described below, with appropriate processconversions.

An amorphous carbon material may be deposited on a conductive materialor conductive portion of a substrate by one or more processes, such asby introducing a gas mixture of one or more hydrocarbon compounds into aprocessing chamber. The hydrocarbon compound may have a formulasubstantially conforming to C_(x)H_(y), where x has ranges between 2 and4 and y ranges between 2 and 10. For example, propylene (C₃H₆), propane(C₃H₈), butane (C₄H₁₀), butylene (C₄H₈), butadiene (C₄H₆), or acetylene(C₂H₂), and/or combinations thereof, may be employed as the hydrocarboncompound.

Alternatively, partially or completely fluorinated derivatives ofhydrocarbon compounds may be employed. For example, the fluorinatedhydrocarbon compounds have a formula substantially conforming toC_(x)H_(y)F_(z), where x ranges between 2 and 4, y ranges between 0 and10, and z ranges between 0 and 10, with y+z greater than or equal to 2and less than or equal to 10. Examples include fully fluorinatedhydrocarbons, such as C₃F₈ or C₄F₈, which may be employed to deposit afluorinated amorphous carbon layer or amorphous fluorocarbon layer. Acombination of hydrocarbon compounds and fluorinated derivatives ofhydrocarbon compounds may also or alternatively be employed to depositthe amorphous layer. Alternatively, hydrocarbon compounds andfluorinated derivatives thereof, including alkanes, alkenes, alkynes,cyclic compounds, and aromatic compounds, having five or more carbons,such as pentane, benzene, and toluene, may be employed to deposit theone or more amorphous layers.

Inert and reactive gases may be added to the gas mixture to modifyproperties of the amorphous material. The gases may be reactive gases,such as hydrogen (H₂), ammonia (NH₃), a mixture of hydrogen (H₂) andnitrogen (N₂), and/or combinations thereof. The addition of H₂ and/orNH₃ can be employed to control the hydrogen ratio of the amorphous layerto control layer properties, such as reflectivity. Inert gases, such asnitrogen (N₂), and noble gases, including Argon (Ar) and Helium (He),may be employed to control the density and deposition rate of theamorphous layer. A mixture of reactive gases and inert gases may also beadded to the processing gas to deposit the amorphous layer.

The amorphous layer may be deposited from the processing gas bymaintaining a substrate temperature ranging between about 100° C. andabout 400° C., such as between about 250° C. and about 400° C.,maintaining a chamber pressure ranging between about 1 Torr and about 20Torr, introducing the hydrocarbon gas (C_(x)H_(y)) and any inert orreactive gases at a flow rate ranging between about 50 sccm and about2000 sccm, and generating a plasma by applying a RF power rangingbetween about 0.03 W/cm² and about 20 W/cm², or between about 10 W andabout 6000 W, for example between about 0.3 W/cm² and about 3 W/cm², orbetween about 100 W and about 1000 W, with a gas distributor beingoffset from the substrate surface by a distance ranging between about200 mils and about 600 mils. The above process parameters provide oneembodiment of a deposition rate for an amorphous carbon layer rangingbetween about 100 Å/min and about 5000 Å/min. The process can beimplemented on a 200 mm substrate in a deposition chamber, althoughothers are also within the scope of the present disclosure.

Alternatively, a dual-frequency system may be employed to deposit theamorphous material. A dual-frequency source of mixed RF power canprovide a high frequency power ranging between about 10 MHz and about 30MHz, as well as a low frequency power ranging between about 100 KHz andabout 500 KHz. An example of a mixed frequency RF power application mayinclude a first RF power with a frequency ranging between about 10 MHzand about 30 MHz at a power ranging between about 200 watts and about800 watts and at least a second RF power with a frequency rangingbetween about 100 KHz and about 500 KHz at a power ranging between about1 watt and about 200 watts. The ratio of the second RF power to thetotal mixed frequency power may range between about 0.6 and about 1.0,although in other embodiments the ratio may be less than about 0.6.

The amorphous layer may comprise carbon and hydrogen atoms, which may bean adjustable carbon:hydrogen ratio that ranges between about 10%hydrogen and about 60% hydrogen. The hydrogen ratio of the amorphouslayer may be controlled to tune the respective optical properties, etchselectivity, and chemical mechanical polishing (CMP) resistanceproperties. As the hydrogen content decreases, the optical properties ofthe as-deposited layer may increase, such as for the index of refractionn and the extinction coefficient k. As the hydrogen content decreases,the etch resistance of the amorphous layer may increase.

The extinction coefficient k of the amorphous layer can be variedbetween about 0.1 and about 1.0 at wavelengths below about 250 nm, suchas between about 193 nm and about 250 nm, which can make the amorphouscarbon layer suitable for use as an anti-reflective coating (ARC) at DUVwavelengths, as well as visible wavelengths. The extinction coefficientk of the amorphous layer can additionally or alternatively be varied asa function of the deposition temperature. For example, as thetemperature increases, the extinction coefficient k of the as-depositedlayer may also increase, such as when propylene is the hydrocarboncompound and the extinction coefficient k for the as-deposited amorphouslayer can be increased from about 0.2 to about 0.7 by increasing thedeposition temperature from about 150° C. to about 480° C.

The extinction coefficient k of the amorphous layer can also be variedas a function of the additive used in the gas mixture. For example, thepresence of hydrogen (H₂), ammonia (NH₃), and nitrogen (N₂), orcombinations thereof, in the gas mixture can increase the extinctioncoefficient k by an amount ranging between about 10% and about 100%.

In an alternate embodiment, the amorphous layer can have an extinctioncoefficient k that varies across the thickness of the layer. That is,the amorphous layer can have an extinction coefficient k gradient formedtherein. Such a gradient may be formed as a function of the variationsof temperature and the composition of the gas mixture during layerformation.

At any interface between two material layers, reflections can occurbecause of differences in their refractive indices n and extinctioncoefficients k. When the amorphous ARC has a gradient, it is possible tomatch the refractive indices n and the extinction coefficients k of thetwo material layers so there is minimal reflection and maximumtransmission into the amorphous ARC. Thereafter, the refractive index nand extinction coefficient k of the amorphous ARC can be graduallyadjusted to absorb all of the light transmitted therein.

The amorphous layer may be deposited as two or more layers havingdifferent optical properties. For example, an amorphous carbon bi-layermay include a first amorphous carbon layer according to the processparameters described above and designed primarily for light absorption.As such, the first amorphous carbon layer may have an index ofrefraction ranging between about 1.5 and about 1.9, and an extinctioncoefficient k ranging between about 0.5 and about 1.0, at wavelengthsless than about 250 nm. A second amorphous carbon layer, such as ananti-reflective coating layer, may be formed on the first amorphouscarbon layer according to the process parameters described above. Assuch, the second amorphous carbon layer may have an index of refractionranging between about 1.5 and about 1.9, and an absorption coefficientbetween about 0.1 and about 0.5. The second amorphous carbon layer maybe designed primarily for phase shift cancellation by creatingreflections that cancel those generated at the interface with anoverlying material layer, such as an energy sensitive resist material.The refractive index n and the extinction coefficient k of the first andsecond amorphous carbon layers may be tunable in that they may be variedas a function of the temperature as well as the composition of the gasmixture during layer formation.

Removal of the amorphous material (whether before or after extraction ofordinary and extraordinary optical characteristics) may be achieved bysubjecting the amorphous layer to a plasma of a hydrogen-containing gasand/or an oxygen-containing gas. The plasma of the hydrogen-containinggas and/or the oxygen-containing gas may remove the amorphous materialwith minimal effect of the dielectric and/or other materials ofunderlying layers.

The plasma treatment may include providing a hydrogen-containing gasincluding hydrogen, ammonia, water vapor (H₂O), or combinations thereof,to a processing chamber at a flow rate ranging between about 100 sccmand about 1000 sccm, such as between about 500 sccm and about 1000 sccm,and generating a plasma in the processing chamber. The plasma may begenerated using a power density ranging between about 0.15 W/cm² andabout 5 W/cm², or an RF power level ranging between about 50 W and about1500 W. The RF power can be provided at a high frequency, such asbetween about 13 MHz and about 14 MHz. The RF power can be providedcontinuously or in short duration cycles wherein the power is on at thestated levels for cycles less than about 200 Hz and the on cycles totalbetween about 10% and about 30% of the total duty cycle.

The plasma treatment may be performed by maintaining a chamber pressureranging between about 1 Torr and about 10 Torr, such as between about 3Torr and about 8 Torr, maintaining the substrate at a temperatureranging between about 100° C. and about 300° C. during the plasmatreatment, such as between about 200° C. and about 300° C., for betweenabout 15 seconds and about 120 seconds, or as necessary to remove theamorphous material with the gas distributor positioned at a distanceranging between about 100 mils and about 2000 mils from the substratesurface, such as a distance ranging between about 200 mils and about1000 mils, during the plasma treatment. However, it should be noted thatthe parameters described above may be modified to perform the plasmaprocesses in various chambers and for different substrate sizes, such asbetween 200 mm and 300 mm substrates. Alternatively, the plasmatreatment process parameters may be the same or substantially the sameas the material deposition process parameters.

In one embodiment, the anisotropic hardmask may be formed by or inconjunction with the APPLIED PRODUCER ADVANCED PATTERNING FILM (APF)PECVD SYSTEM that is commercially available from APPLIED MATERIALS, INC.The APPLIED PRODUCER APF system can be used, for example, to form astrippable hardmask on a substrate. The APPLIED PRODUCER APF system canform a dual layer stack consisting of a thin amorphous carbon layer witha thin DARC cap layer. The resulting CVD amorphous carbon hardmask canbe highly selective for polysilicon and oxide etching withpoly-to-carbon selectivity as high as 6:1, and oxide-to-carbonselectivity of 15:1. The APF may be easily stripped in an oxygen plasmaash, and both the carbon and DARC bi-layer may work as ananti-reflective coating for both 248 nm and 193 nm photolithography. TheAPF hardmask can be performed with as little as 100 nm of photoresist.In addition, the APF deposition process can eliminate the need for thewet chemical processing and treatment that are conventionally used inmulti-layer resist process.

The method 300 also includes a step 320 in which the ordinary refractiveindex n_(o) and the ordinary extinction coefficient k_(o) are extracted,as well as a step 330 in which the extraordinary refractive index n_(e)and the extraordinary extinction coefficient k_(e) are extracted.However, as described above, the ordinary and extraordinarycharacteristics may be extracted substantially simultaneously. Theordinary refractive index n_(o) may be regarded as the speed ofpropagation in the plane of incidence, the plane of greatest speed ofpropagation, and/or another plane/direction. In any case, theextraordinary refractive index n_(e) may be regarded as the speed ofpropagation in a substantially different plane or direction, such as ina plane or direction that is substantially orthogonal to that of theordinary refractive index n_(o). For example, in one embodiment, theordinary refractive index n_(o) corresponds to the p-direction and theextraordinary refractive index n_(e) corresponds to the s-direction, asdescribed above with reference to FIG. 2. The ordinary and extraordinaryextinction coefficients k_(o) and k_(e) may be similarly related.

In the embodiment depicted in FIG. 7, the ordinary and extraordinarycharacteristics n_(o), n_(e), k_(o) and k_(e) are extracted after thehardmask is substantially completed, but prior to use of the hardmask toetch underlying layers. However, in other embodiments, the opticalcharacteristics of the hardmask may be extracted prior to the completionof the hardmask, as well as after one or more etching processes havebeen initiated and/or completed.

Referring to FIG. 8, illustrated is a flow-chart diagram of anotherembodiment of the method 300 shown in FIG. 7, herein designated by thereference numeral 305. The method 305 is substantially similar to themethod 300 shown in FIG. 7, in that the method 305 includes the steps310, 320 and 330 described above. However, the method 305 also includesa step 340 in which the ordinary and extraordinary characteristicsn_(o), n_(e), k_(o) and k_(e) are input into an optical criticaldimension (OCD) model. The OCD model may describe the geometricdimensions and/or optical characteristics of the hardmask, one or morelayers underlying the hardmask, and/or one or more features definedduring etch processing employing the hardmask. In one embodiment, theOCD model accounts for all layers in the sample structure beingcharacterized, measured, or verified by the optical CD measuring system.The OCD model may be subsequently employed in a step 350 during whichcritical dimensions (CDs) of the hardmask and/or underlying features areoptically verified. The optically-verified CDs may then be verified viaa scanning electron microscope (SEM) in a step 360.

Referring to FIG. 9, illustrated is a schematic view of at least aportion of one embodiment of apparatus 400 according to one or moreaspects of the present disclosure. The apparatus 400, which maygenerally resemble a cluster tool, may be employed with or during themethod 300 shown in FIG. 7 and/or the method 305 shown in FIG. 8. Thatis, the apparatus 400 may be employed to verify CDs of a hardmask orother features formed on a substrate, including those formed within theapparatus 400.

The apparatus 400 includes four process chambers 410, although otherembodiments may include more or less than four process chambers 410.Each process chamber 410 is configured to perform one or moresemiconductor fabrication processes, such as deposition and/or etchingprocesses. For example, each chamber 410 may be configured to performchemical vapor deposition (CVD), plasma enhanced CVD (PECVD), and/orphysical vapor deposition (PVD), among others. One or more of thechambers 410 may additionally or alternatively be configured to performrapid thermal annealing and/or other heat treatment processes.

The apparatus 400 also includes wafer transfer means 420 housed within acentral chamber or staging area 405. The wafer transfer means 420 areconfigured to transfer process wafers between the chambers 410 andload-lock means 430. The wafer transfer means 420 and/or the load-lockmeans 430 may be partially or fully automated.

The apparatus 400 also includes CD measurement means 440. The CDmeasurement means 440 may be integral to the apparatus 400 such that CDsof features on wafers processed within the apparatus 400 may be examinedwithout requiring the removal of the wafer from the apparatus 400. Thatis, the CD measurement means 440 may be configured to perform in-situ CDmeasurement. Methods by which CDs may be measured via CD measurementmeans 440 may be substantially similar to those described above,including via the extraction of both ordinary and extraordinary opticalcharacteristics. The CD measurement means 440 may include optical and/orSEM CD measurement means, among others, including those described above(e.g., with respect to FIGS. 3-6).

In the embodiment depicted in FIG. 9, the CD measurement means 440 areintegral to the load-lock area of the apparatus 400. Consequently, CDmeasurements may be performed prior to and/or after one or moreprocesses are performed within the apparatus 400, including atintermediate points between processes.

Referring to FIG. 10, illustrated is a schematic view of at least aportion of another embodiment of the apparatus 400 shown in FIG. 9,herein designated by the reference numeral 450. The apparatus 450 issubstantially similar to the apparatus 400 shown in FIG. 9, such as inthe similar inclusion of a number of process chambers 410, wafertransfer means 420, load-lock means 430 and CD measurement means 440.However, the CD measurement means 440 of apparatus 450 is externallycoupled to the load-lock means 430, in contrast to the integralarrangement of apparatus 400. Nonetheless, CD measurement may still beperformed in-situ, as the load-lock means 430 may be configured totransfer wafers to and from the CD measurement means 440.

Referring to FIG. 11, illustrated is a schematic view of at least aportion of another embodiment of the apparatus 400 shown in FIG. 9,herein designated by the reference numeral 460. The apparatus 460 issubstantially similar to the apparatus 400 shown in FIG. 9, such as inthe similar inclusion of a number of process chambers 410, wafertransfer means 420, load-lock means 430 and CD measurement means 440.However, the CD measurement means 440 of apparatus 460 is externallycoupled to the center chamber 405, in contrast to the arrangement ofapparatus 400. Nonetheless, CD measurement may still be performedin-situ, as the wafer transfer means 420 may be configured to transferwafers to and from the CD measurement means 440.

Referring to FIG. 12, illustrated is a flow-chart diagram of at least aportion of one embodiment of a method 500 according to aspects of thepresent disclosure. The method 500 is one example of operations that maybe performed via the apparatus 400, 450 and/or 460 shown in FIGS. 9-11,among others within the scope of the present disclosure. One or moreaspects of the method 500 may be substantially similar to those of themethods 300 and 305 shown in FIGS. 7 and 8, among others within thescope of the present disclosure.

The method 500 includes a step 505 in which an amorphous carbon or otheranisotropic hardmask is formed on a wafer. Aspects of the step 505 maybe substantially similar to those of step 310 shown in FIGS. 7 and 8,and may include processing/operations within one or more chambers of acluster tool, such as the chambers 410 of the apparatus 400, 450 and 460shown in FIGS. 9-11.

In a subsequent step 510, the wafer is transferred to a CD measurementtool. For example, wafer transfer means (e.g., wafer transfer means 420shown in FIGS. 9-11) and/or load-lock means (e.g., load-lock means 430shown in FIGS. 9-11) may independently or cooperatively transfer thewafer to a CD measurement tool (e.g., CD measurement means 440 shown inFIGS. 9-11) which may be integral to or coupled to the apparatus inwhich the wafer is being processed. Thereafter, the CD measurement toolmay be employed to extract the ordinary index of refraction n_(o) andextinction coefficient k_(o) of a hardmask and/or one or more otherfeatures and/or layers on the wafer during a step 515, possiblyincluding several such measurements (e.g., time- and/orwavelength-dependent measurements). Step 515 may be substantiallysimilar to step 320 shown in FIGS. 7 and 8.

While the wafer is in the CD measurement tool, the extraordinary indexof refraction n_(e) and extinction coefficient k_(e) of the hardmask,feature(s) and/or layer(s) on the wafer may also be extracted during astep 520, possibly including several such measurements (e.g., time-and/or wavelength-dependent measurements). Step 520 may be substantiallysimilar to step 330 shown in FIGS. 7 and 8. Moreover, at least in oneembodiment, steps 515 and 520 may be performed substantiallysimultaneously.

In a subsequent step 525, one or more process recipes for trimming,etching and/or otherwise processing the hardmask, feature(s) and/orlayer(s) on the wafer are selected, calculated or otherwise determined,based on the optical characteristics extracted during steps 515 and 520.The wafer is then transferred to an etching or other processing tool instep 530, where such tool may be substantially similar to one of thechambers 410 shown in FIGS. 9-11, and where such transfer may beperformed by means such as wafer transfer means 420 and/or load-lockmeans 430 also shown in FIGS. 9-11. The hardmask, feature(s) and/orlayer(s) on the wafer may then be trimmed in a step 535, etched in astep 540, or otherwise processed, possibly based on the opticalcharacteristics extracted during steps 515 and 520.

The wafer may subsequently be transferred to a stripping tool in a step545, such as via wafer transfer means 420 and/or load-lock means 430shown in FIGS. 9-11. The stripping tool may be a chamber of a clustertool, such as one of the chambers 410 shown in FIGS. 9-11. Thereafter, astep 550 may be performed to remove at least a portion of one or more ofthe hardmask, feature(s) and/or layer(s) on the wafer. For example, step550 may include plasma ashing, in which oxygen and a fluorocarbon (e.g.,CF₄ or C₂F₆) are employed to strip the hardmask from the wafer. Thestripping tool may be or include a plasma etch tool, such as a barreltype tool where a plasma is generated in the same chamber as thesubstrate, or a downstream type tool in which a plasma is generated inone chamber and is directed towards the wafer in a second chamberthrough a tube or an inlet. The plasma source may be an inductivelycoupled plasma (ICP) source or a transformer coupled plasma (TCP)source, among others.

An oxygen plasma may be employed to strip the hardmask and/or otherfeature(s) on the wafer since the oxygen radicals react with C, H, S,and N in polymer and photosensitive material components to afford theirrespective oxides, which are volatile. However, pure O₂ plasma may notalways sufficiently strip the hardmask and/or other feature(s) on thewafer, such that C₂F₆ may be combined with O₂ in a first plasma etchstep and then followed with an O₂-only ashing step to more thoroughlyremove the hardmask and/or other feature(s) on the wafer. In oneembodiment, water is employed as an oxygen and hydrogen source andcombined with CF₄ in a first plasma ash step and O₂ plasma is then usedin a second step to complete the stripping process.

The stripping performed during step 550 may also or alternativelyinclude a low-temperature stripping method, such as may involve anoxidizing gas, a halide containing gas and a hydrocarbon. One suchembodiment may utilize SO₃ by itself or combined with oxygen and/orother etching gases. For example, a low-temperature hardmask stripprocess involving O₂ and a fluorocarbon plasma etch may be employed.

In one embodiment, the stripping performed in step 550 may employ aplasma treatment which includes oxygen and one or more fluorocarbongases C_(X)H_(Y)F_(Z) where x, y and z are integers, such as CH₃F,CH₂F₂, and CHF₃. Furthermore, the gas mixture used to generate theplasma may be additionally comprised of N₂ or N₂H₄. Optionally, theplasma treatment is performed without oxygen.

As an example of the stripping performed during step 550, the wafer maybe fastened to a chuck in a process chamber that is part of thestripping tool, and a vacuum is applied to remove all gases from theprocess chamber. Plasma may be generated in the chamber from an RFdischarge source and bias power, or from a microwave downstream plasmaflow, as in an asher. However, other chamber architectures and plasmadelivery systems are also within the scope of the present disclosure.The plasma may be generated in the process chamber by first purging thechamber and subsequently introducing oxygen, possibly at a flow rateranging between about 200 and about 10,000 sccm, and one or moreC_(X)H_(Y)F_(Z) gases, such as CH₃F, CH₂F₂, and CHF₃ each with a flowrate ranging between about 1 and about 500 sccm, all flowed into theprocess chamber while the wafer is heated to a temperature rangingbetween about 20° C. and about 300° C. The ratio of oxygen flow rate toC_(X)H_(Y)F_(Z) flow rate may range between about 10:1 and about 1000:1.The combined gas flow may provide a pressure range between about 10mtorr and about 5 torr in the process chamber. Once the desiredtemperature is reached, a plasma can be struck by applying an RF powerranging between about 200 W and about 2000 W. The plasma treatment iscontinued while the temperature is maintained between about 20° C. andabout 300° C. for a predetermined amount of time or until end pointdetection. The wafer may subsequently be cleaned with a DI-rinse and/orother cleaning methods.

In a step 555, the wafer may be transferred to a CD measurement tool, asdescribed above with respect to step 510. One or more CDs of theunderlying layer that was patterned with the hardmask may be measured ina subsequent step 560. If additional processing is required, such as maybe indicated by the results of the measurements taken during step 560,one or more of steps 525-555 may be repeated. However, the method mayalternatively proceed to a step 565, during which the wafer may betransferred for additional processing, whether within the same apparatusor other apparatus.

Referring to FIG. 13, illustrated is a flow-chart diagram of anotherembodiment of the method 500 shown in FIG. 12, herein designated by thereference numeral 600. The method 600 includes one or more lithographysteps 610 during which one or more layers of photoresist material arepatterned, one or more etching steps 615 during which the pattern of oneor more layers is transferred to one or more underlying metal and/ordielectric layers, and one or more deposition steps 620 during which oneor more photoresist, metal and/or dielectric layers are formed over awafer or substrate. The one or more deposition steps 620 may includeperforming one or more CVD processes 625, one or more PVD processes 630,one or more growth processes 635 (e.g., in-situ growth, selectiveepitaxial growth, and others), one or more thermal treatment processes640 (e.g., rapid-thermal-annealing, and others), and/or one or moreplating processes 645 (e.g., electroplating, silicide formation, andothers).

The method 600 may also include one or more stripping steps 650 duringwhich at least portions of one or more previously-formed layers areremoved, as well as one or more cleaning steps 655 during which residue,particulate and/or contaminants may be removed by one or more wet or dryprocesses. The method 600 may also include one or more planarizing steps660 during which one or more previously-formed layers may be chemicallyand/or mechanically planarized (e.g., CMP) to provide substantiallyplanar surfaces, such as in preparation for subsequent processing.

The method 600 also includes at least one CD measurement step 670interposing ones of the above-described steps 610, 615, 620, 650, 655and 660, as indicated by the dashed arrows schematically interconnectingthese steps. The CD measurement step 670 include measurement byapparatus having one or more aspects that are substantially similar tothose of apparatus shown in FIGS. 3-6 and/or 9-11. The CD measurementstep 670 may also or alternatively include measurement by one or moremethods having one or more aspects that are substantially similar tothose of steps 320 and 330 shown in FIG. 7, steps 320-360 shown in FIG.8, and/or steps 515, 520 and 560 shown in FIG. 12.

For example, as in the embodiment depicted in FIG. 13, the method 600may include a CD measurement step 670 interposing the one or morelithography steps 610 and the one or more etch steps 615, such that themethod 600 may proceed from lithography to CD measurement and then toetching, in contrast to proceeding from lithography directly to etching.Similarly, the method 600 may also or alternatively include a CDmeasurement step 670 interposing the one or more etch steps 615 and theone or more stripping steps 650 (when performed), such that the method600 may proceed from etching to CD measurement and then to stripping, incontrast to proceeding from etching directly to stripping. The method600 may also or alternatively include a CD measurement step 670interposing the one or more stripping steps 650 (when performed) and theone or more cleaning steps 655 (when performed), such that the method600 may proceed from stripping to CD measurement and then to cleaning,in contrast to proceeding from stripping directly to cleaning.

The method 600 may also or alternatively include a CD measurement step670 interposing the one or more cleaning steps 655 (when performed) andthe one or more deposition steps 620, such that the method 600 mayproceed from cleaning to CD measurement and then to deposition, incontrast to proceeding from cleaning directly to deposition. The method600 may also or alternatively include a CD measurement step 670interposing the one or more deposition steps 620 and the one or moreplanarizing steps 660 (when performed), such that the method 600 mayproceed from deposition to CD measurement and then to planarization, incontrast to proceeding from deposition directly to planarization. Themethod 600 may also or alternatively include a CD measurement step 670interposing the one or more planarizing steps 660 (when performed) andthe one or more lithography steps 610, such that the method 600 mayproceed from planarizing to CD measurement and then to lithography, incontrast to proceeding from planarizing directly to lithography.

The cycle of lithography 610, etch 615, strip 650 (when performed),clean 655 (when performed), deposition 620 and planarization 660 (whenperformed) may be repeated a number of times during the manufacture ofan integrated circuit device. Each such cycle may result in theformation of a hardmask or other photoresist layer, a metal layer, adielectric layer, and/or a semiconductor layer, or multiples thereof,including where such layers may ultimately define a number of discretemembers or otherwise be patterned. However, each cycle may not includethe same sequence of steps 610-615-650-655-620-660, as some cycles mayexclude one or more of such steps, may include a different sequence,and/or may include additional steps not illustrated in FIG. 13. Inaddition, each cycle may not include a CD measurement step 670 betweeneach of the steps 610-615-650-655-620-660 in a particular sequence. Forexample, one or more cycles may include only one or two CD measurementsteps 670, whereas other cycles may include a greater number of CDmeasurement steps 670, and one or more other cycles may not include anyCD measurement steps 670.

It is evident from the description above and the following claims thatthe present disclosure introduces a method of measuring a criticaldimension of an optically-anisotropic feature, the method comprisingextracting a number of values each descriptive of theoptically-anisotropic feature, including values corresponding toordinary and extraordinary measurements of one or more opticalcharacteristics of the optically-anisotropic feature. The opticalcharacteristics can include the index of refraction and/or theextinction coefficient of the optically-anisotropic feature, amongothers. Additionally, the values can be input into an optical criticaldimension (OCD) measurement model, such that the critical dimension canbe verified via optical measurement based on the OCD measurement model.The optical measurement of the critical dimension can also be verifiedvia scanning electron microscope (SEM) measurement. Furthermore, theoptically-anisotropic feature may have a substantially amorphouscomposition, such as amorphous carbon, including where theoptically-anisotropic feature is that of a hardmask substantiallycomprising amorphous carbon or otherwise having a substantiallyamorphous composition.

Another embodiment of a method of measuring a critical dimension of anoptically-anisotropic feature according to aspects of the presentdisclosure includes extracting a first optical characteristic of theoptically-anisotropic feature, wherein the first optical characteristicis one of an ordinary index of refraction and an ordinary extinctioncoefficient of the optically-anisotropic feature. The method alsoincludes extracting a second optical characteristic of theoptically-anisotropic feature, wherein the second optical characteristicis one of an extraordinary index of refraction and an extraordinaryextinction coefficient of the optically-anisotropic feature.

For example, the first optical characteristic may be the ordinary indexof refraction of the optically-anisotropic feature and the secondoptical characteristic may be the extraordinary index of refraction ofthe optically-anisotropic feature. In another example, the first opticalcharacteristic may be the ordinary extinction coefficient of theoptically-anisotropic feature and the second optical characteristic maybe the extraordinary extinction coefficient of the optically-anisotropicfeature.

The method may also include extracting a third optical characteristic ofthe optically-anisotropic feature. In one embodiment, the third opticalcharacteristic is one of the ordinary extinction coefficient and theextraordinary extinction coefficient of the optically-anisotropicfeature, while in another embodiment the third optical characteristic isone of the ordinary index of refraction and the extraordinary index ofrefraction of the optically-anisotropic feature. The method may alsoinclude extracting a fourth optical characteristic of theoptically-anisotropic feature, such that the first, second, third andfourth optical characteristics collectively include the ordinary andextraordinary indices of refraction and extinction coefficients of theoptically-anisotropic feature.

The present disclosure also introduces a cluster tool operable in thefabrication of a microelectronic device. In one embodiment, the clustertool includes a plurality of integrated process chambers each configuredto process a wafer. The cluster tool also includes means for opticallymeasuring a critical dimension of an optically-anisotropic featureformed on the wafer without removing the wafer from the cluster tool,including means for extracting ordinary and extraordinary opticalcharacteristics of the optically-anisotropic feature. The cluster toolalso includes means for transferring the wafer between ones of theprocess chambers and the critical dimension measuring means. In oneembodiment, the plurality of process chambers includes at least onechamber operable to form a substantially amorphous hardmask comprisingthe optically-anisotropic feature, as well as at least one chamberoperable for ash-removal of the hardmask. At least one chamber may beoperable to form an amorphous carbon hardmask comprising theoptically-anisotropic feature. The cluster tool may also include meansfor loading and unloading the wafer into a wafer staging area of thecluster tool, wherein the critical dimension measuring means is integralto the loading and unloading means.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions andalterations herein without departing from the spirit and scope of thepresent disclosure.

1. A method of measuring a critical dimension of anoptically-anisotropic feature, comprising: extracting a first valuedescriptive of the optically-anisotropic feature; and extracting asecond value descriptive of the optically-anisotropic feature, whereinthe first value corresponds to an ordinary measurement of an opticalcharacteristic of the optically-anisotropic feature, and the secondvalue corresponds to an extraordinary measurement of the opticalcharacteristic of the optically-anisotropic feature; analyzing the firstand second values using an optical critical dimension (OCD) measurementmodel; and verifying the critical dimension via optical measurementbased on the analyzing using the OCD measurement model.
 2. The method ofclaim 1 wherein the optical characteristic is one of: an index ofrefraction of the optically-anisotropic feature, and an extinctioncoefficient of the optically-anisotropic feature.
 3. The method of claim1 further comprising extracting third and fourth values descriptive ofthe optically-anisotropic feature, wherein: the first value correspondsto an ordinary measurement of an index of refraction of theoptically-anisotropic feature, the second value corresponds to anextraordinary measurement of the index of refraction of theoptically-anisotropic feature, the third value corresponds to anordinary measurement of an extinction coefficient of theoptically-anisotropic feature, and the fourth value corresponds to anextraordinary measurement of the extinction coefficient of theoptically-anisotropic feature.
 4. The method of claim 1 furthercomprising verifying the optical measurement of the critical dimensionvia scanning electron microscope (SEM) measurement.
 5. The method ofclaim 1 wherein the optically-anisotropic feature has a substantiallyamorphous composition.
 6. The method of claim 1 wherein theoptically-anisotropic feature substantially comprises amorphous carbon.7. The method of claim 1 wherein the optically-an isotropic feature is ahardmask having a substantially amorphous composition.
 8. The method ofclaim 1 wherein the optically-anisotropic feature is a hardmasksubstantially comprising amorphous carbon.
 9. A method of measuring acritical dimension of an optically-anisotropic feature, comprising:extracting a first optical characteristic of the optically-anisotropicfeature, wherein the first optical characteristic is one of an ordinaryindex of refraction of the optically-anisotropic feature, and anordinary extinction coefficient of the optically-anisotropic feature;and extracting a second optical characteristic of theoptically-anisotropic feature, wherein the second optical characteristicis one of: an extraordinary index of refraction of theoptically-anisotropic feature, and an extraordinary extinctioncoefficient of the optically-anisotropic feature; analyzing the firstand second values using an optical critical dimension (OCD) measurementmodel; and verifying the critical dimension via optical measurementbased on the analyzing using the OCD measurement model.
 10. The methodof claim 9 wherein: the first optical characteristic is the ordinaryindex of refraction of the optically-anisotropic feature, and the secondoptical characteristic is the extraordinary index of refraction of theoptically-anisotropic feature.
 11. The method of claim 10 furthercomprising extracting a third optical characteristic of theoptically-anisotropic feature, wherein the third optical characteristicis one of: the ordinary extinction coefficient of theoptically-anisotropic feature, and the extraordinary extinctioncoefficient of the optically-anisotropic feature.
 12. The method ofclaim 11 further comprising extracting a fourth optical characteristicof the optically-anisotropic feature, wherein: the third opticalcharacteristic is the ordinary extinction coefficient of theoptically-anisotropic feature, and the fourth optical characteristic isthe extraordinary extinction coefficient of the optically-anisotropicfeature.
 13. The method of claim 9 wherein: the first opticalcharacteristic is the ordinary extinction coefficient of theoptically-anisotropic feature, and the second optical characteristic isthe extraordinary extinction coefficient of the optically-anisotropicfeature.
 14. The method of claim 13 further comprising extracting athird optical characteristic of the optically-anisotropic feature,wherein the third optical characteristic is one of: the ordinary indexof refraction of the optically-anisotropic feature, and theextraordinary index of refraction of the optically-anisotropic feature.15. A cluster tool operable in the fabrication of a microelectronicdevice, comprising: a plurality of integrated process chambers eachconfigured to process a wafer: means for optically measuring a criticaldimension of an optically-anisotropic feature formed on the waferwithout removing the wafer from the cluster tool, including means forextracting ordinary and extraordinary optical characteristics of theoptically-anisotropic feature, wherein the critical dimension measuringmeans is coupled to a central chamber comprising a transfer chamber; andmeans for transferring the wafer between ones of the process chambersand the critical dimension measuring means.
 16. The cluster tool ofclaim 15 wherein the plurality of process chambers includes: at leastone chamber operable to form a substantially amorphous hardmaskcomprising the optically-anisotropic feature, and at least one chamberoperable for ash-removal of the hardmask.
 17. The cluster tool of claim15 wherein the plurality of process chambers includes at least onechamber operable to form an amorphous carbon hardmask comprising theoptically-anisotropic feature.
 18. The cluster tool of claim 15 furthercomprising means for loading and unloading the wafer into a waferstaging area of the cluster tool, wherein the critical dimensionmeasuring means is integral to the loading and unloading means.